The long term goal of the proposed research is to obtain a full understanding of the complexation chemistry associated with lanthanide complexes of nucleotides and nucleic acids. These compounds are quite important since the luminescence properties of the TB(III) derivatives have been found to be extremely sensitive toward chemical modification of the heterocyclic bases. Therefore, any detailed understanding of these photophysical processes requires an evaluation of how Tb (III) and nucleic acids interact, and how these interactions affect the photophysical properties of the TB(III) ion. We propose here to obtain this required information through studies of TB(III) complexes of nucleosides, nucleotides, and nucleic acids. The nucleotide and nucleoside compounds are intended to serve as model systems in which the full range of possible metalligand interactions may be detailed. Supporting structural information will be obtained from single crystal x-ray structure determinations and computer molecular modeling utilizing molecular mechanics energy minimum energy conformations and display of selected model systems, and thus correlations between TB(III) photophysics and structure determinations. will be developed. The nucleic acid work will include some effort with short-chain oligonucleotides. The performance of the proposed research will, therefore, place the use of Tb(III) luminescence into the range of techniques suitable for probing the structure of certain oligonucleotides, and will provide the basis for using this technique on a more quantitative level.